Romulox is a fanged humanoid tar monster, the "ruler of the tar creatures", Shake's "arch enemy" and an arrogant hipster tech-snob who first appeared in the episode PDA.
Master Shake claims to have lost his Personal Data Assistant, eventually blaming it on Romulox, who he calls his arch enemy and remembered having last seen at the Trenton Tar Pits. When the Aqua Teens arrive, they search for him under the tar in a run-down tourist submarine with a convicted sex offender as the tour guide. Seeing nothing out the windows but "tar and a condom wrapper" as Frylock notes to his disgust, they head home. When they get home they find a strange looking humanoid tar monster sporting a two-piece bikini and fingerless gloves inside their house who Shake identifies as Romulox.
Despite being a tar monster, Romulox is known for his arrogant, bored hipster attitude ("Look, I'm better than you, okay? I just am.") and vast number of trendy technical gadgets, including a thought-activated, teleportation-capable PDA that he freely pawns off on Shake, dismissing it as "old" and saying it "makes him look like a hillbilly". He also sports a grappling hook and an "Easy Flow Elbow", which he claims only two people in the world have, and "one of them happens to be Bruce Willis...."
Romulox could have possibly died in the episode The Last One, where he finished off the last few parts of The Broodwich (the sun-dried tomatoes), which sent him to the Broodwich Dimension. He never returned after this scene.